[PHP-WEBMASTER] [web-php] PR #954: Fix: Move cache file to `.build/php-cs-fixer/`

[localheinz]

Pull Request: https://github.com/php/web-php/pull/954
Author: localheinz

This pull request

- [x] moves the cache file for `friendsofphp/php-cs-fixer` to 
`.build/php-cs-fixer/`